User:Mariel Feliciano

Glucose/Galactose-binding protein


Glucose/Galactose-binding protein (GGBP) from E. coli is found in the periplasm of the bacterium. This protein is involved in the transport of glucoseas well as the chemotaxis toward it. It is composed of two Rossman folds separated by three short segments of amino acids termed the "hinges" because of their role in the opening/closing mechanism of the protein. The protein exists in two conformations: glucose-bound (closed) and unbound (open) (Figure 1). Upon ligand binding, changes in the torsional angles of the amino acids that compose the hinges produce a conformational change between the two domains that stabilize the closed conformation. Analysis of the structure with Consurf (Figure 2) shows that amino acids that line the binding site and amino acids that compose the hinges are the most conserved. Despite its homology with other sugar-binding proteins like ribose-binding protein (RBP), the changes in torsional angles of the amino acids that compose the hinges and trigger the conformational changes between domains differ in both proteins. One of the structures reported by Borrok, M.J., Kiessling, L.L.,  and Forest, K.T. (PDB ID 2FW0) is the first crystal structure of the protein in its open conformation. The other structure reported by these authors (PDB ID 2FVY) is an ultra-high resolution (0.95Å) crystal structure of the glucose-bound protein.



Scenes



 * Binding site showing most conserved residues as defined by Consurf
 * Close-up view of one of the protein's two domains (Rossman folds)
 * Three-segment hinge region

